Normalizing structure for intro section of various books #2814
Description
In the filesystem book the intro duplicates info available in the setup.xml file.
It also seems that we are pretty inconsistent about the structure of various books in what is included or not (e.g. some extensions that don't have resources don't mention them at all, which is a direction which makes sense to take as we are getting rid of them).
Originally posted by @Girgias in #2726 (comment)